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Re: <details> element clarifications

From: Andrea Rendine <master.skywalker.88@gmail.com>
Date: Tue, 11 Nov 2014 21:03:31 +0100
Message-ID: <CAGxST9nn=AXJGQRUUSTG9aJrEbQtCK0B2cwGqFCB7xsQn=Oo-Q@mail.gmail.com>
To: public-html@w3.org, Maksim Chemerisuk <chemerisuk@gmail.com>
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2014-11-11 19:56 GMT+01:00 Maksim Chemerisuk <chemerisuk@gmail.com>:

> Thanks for clarification Andrea, I guess you answered all my questions. I
> was confused by the definition from the spec because browser vendors use
> :first-of-type CSS selector to catch <summary>, not :first-child. It looks
> like they just try to fix such invalid markup. In my case I decided to move
> the element to the first child position to avoid such confusing
> presentation.
> Will this conversion be published somewhere, so I can reference to it?
> ---
> Maksim
> On 11 November 2014 18:35, Andrea Rendine <master.skywalker.88@gmail.com>
>  wrote:
>> Hi again Maxim.
>> I re-read your definition. Better to clarify that point first.
>> At this moment, no definition state that it is correct to put summary as
>> second, third etc. child element of <details>.
>> *The first summary element child of the element, if any, represents the
>> summary or legend of the details. If there is no child summary element, the
>> user agent should provide its own legend (e.g. "Details").*
>> This sentence only states one thing: if by mistake <details> contains
>> more than 1 <summary> child element, only the first is meant to be the
>> legend for the widget.
>> The only allowed subtree for this element is:
>> - details
>>    - summary
>>    - [other flow content]
>> while content rearrangement mechanics must be seen only as error handling
>> (in some sense, as browsers handle incorrect nesting for paragraphs and
>> text formatting.
>> So of course all issues regarding content flow must take into account
>> that putting <summary> after other flow elements is, by any mean,
>> incorrect, and as such doesn't deserve any other rule for displaying.
>> In my opinion it would have been much better for spec authors to state
>> that a <details> should have a summary attribute, not element, so that its
>> text value could be displayed as the element's legend. But i suppose that
>> it was meant for legacy user agents who wouldn't have known how to display
>> a new attribute.
>> Summarizing:
>>    - the only correct DOM subtree for the element is the one stated
>>    above.
>>    - definition 1 states that,
>>    - if more than 1 summary element is present, then only the first must
>>    be considered.
>>    - the first summary element is the <details>' legend, thus opening
>>    way to error handling.
>>    - both these statements are edge cases and incorrect. But authors
>>    still ignore correctedness several times.
>>    - definition 2 is currently the correct way.
>> Thank you for the note about Safari. I reported you what Steve Faulkner
>> stated:
>> http://lists.w3.org/Archives/Public/public-html/2014Nov/0039.html
>> No doubt I will reply to his message, now that you mention it.
>> Bye!
>> Andrea
>> 2014-11-11 14:22 GMT+01:00 Maksim Chemerisuk <chemerisuk@gmail.com>:
>>> Thanks for the response Andrea.
>>> Does it really make sense to allow <summary> NOT to be the first child
>>> and then fix it visually? From what I understood HTML allows such kind of
>>> markup, but not XHTML. I believe it will be much clearer to fix the problem
>>> in the definition, because such edge case makes harder creating a polyfill.
>>> Moreover a display result may look confusing, because normal element flow
>>> is different from rendered result, where <summary> is always on the top of
>>> <details> even it's not the first child (this is what we have at present in
>>> WebKit actually). Any reasons why it wasn't defined in this way?
>>> I checked http://validator.w3.org/nu/ too, it looks like it works
>>> according to the <summary> context definition: only first child is allowed.
>>> Does it mean that this is the correct markup then? If yes, I do suggest to
>>> fix the confusing definition I mentioned in the first email.
>>> The argument for the second question is clearer, thanks.
>>> BTW you can count Safari as another one browser that supports <details>:
>>> http://caniuse.com/#feat=details
>>> ---
>>> Thanks,
>>> Maksim
>>> On 11 November 2014 04:33, Andrea Rendine <master.skywalker.88@gmail.com
>>> > wrote:
>>>> Sidenote: Validator.w3.org/nu <http://validator.w3.org/nu> does not
>>>> flag <details> as not allowed, yet. Or already, as it will be probably
>>>> allowed when UAs restore support. It flags its use as "not advised because
>>>> of poor implementation", though.
>>>> Anyway, it considers an error to put elements before the <summary>.
>>>> Both Opera and Chrome display it correctly when the order is messed (Opera
>>>> still supports <details>. Great.)
>>>> Bye.
>>>> 2014-11-11 2:24 GMT+01:00 Andrea Rendine <master.skywalker.88@gmail.com
>>>> >:
>>>>> Hi Maksim.
>>>>> For what I remember, in the WHATWG version of the spec it was
>>>>> explicitly stated that <summary> can be something different than the very
>>>>> first child element of a <details>. I tried to wayback the page, but
>>>>> there's nothing old enough to support my statement. Anyway i guess their
>>>>> living standard had tree construction rules for repositioning the first
>>>>> <summary> child element as first element inside <details>. It must be so,
>>>>> because toggling the show/hide action, the rest of the <details> content is
>>>>> shown below the summary, so ideally the element must be first.
>>>>> It's almost the same than <table><tbody><tr> issue (it isn't correct
>>>>> to put <tr> directly inside <table>. Thus said, browsers know what to do
>>>>> and build fake <tbody>s wrapping rows).
>>>>> As for the second question, consider that the purpose of <details> is
>>>>> not semantic, but strictly presentational: it represents a collapsible
>>>>> widget. So it MUST have a control for the collapse/espand action. If the
>>>>> author doesn't insert it by himself, the browser has to work it around.
>>>>> Of course these answers only apply to HTML. XHTML document DOM trees
>>>>> cannot be changed, so the element must a) be present and b) be first.
>>>>> A last point: <details> has very poor implementation, for what I know
>>>>> at this very moment only Google Chrome latest release supports it. It has
>>>>> also been removed from W3 HTML5 Recommendation, due to the lack of at least
>>>>> 2 interoperable implementations.
>>>>> Hope this helped.
>>>>> Regards.
>>>>> Andrea R.
>>>>> 2014-11-09 22:18 GMT+01:00 Maksim Chemerisuk <chemerisuk@gmail.com>:
>>>>>> Hi guys,
>>>>>> I'm writing an article about <details> element polyfil and after
>>>>>> reading the specification at
>>>>>> http://www.w3.org/html/wg/drafts/html/master/interactive-elements.html#the-details-element want
>>>>>> to clarify some parts in it.
>>>>>> *The first summary element child of the element, if any, represents
>>>>>> the summary or legend of the details. If there is no child summary element,
>>>>>> the user agent should provide its own legend (e.g. "Details").*
>>>>>> 1)
>>>>>> The first definition of <summary> assumes that it may NOT be the
>>>>>> first child of <details>. Later, I found a correction at
>>>>>> http://www.w3.org/html/wg/drafts/html/master/interactive-elements.html#the-summary-element
>>>>>> :
>>>>>> *Contexts in which this element can be used:*
>>>>>> *As the first child of a details element.*
>>>>>> So what's the correct answer then? Is it valid for the <summary>
>>>>>> element not to be the first child?As far as I see in Webkit implementation
>>>>>> allows that.
>>>>>> 2)
>>>>>> What's the goal of adding fake "Details" legend if <details> does not
>>>>>> contain a child <summary>? It's a bit weird so I'd like to understand this
>>>>>> edge case better to be as much complied to the spec as possible.
>>>>>> Thanks!
>>>>>> ---
>>>>>> Maksim Chemerisuk
Received on Tuesday, 11 November 2014 20:03:59 UTC

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